DBF, you will probably read this post with disgust and I apologise in advance. We used to euthanise 10 - 15 dogs per week, mainly staffs and greyhounds. In the main, they were healthy, very friendly dogs. The owner of the "rescue kennels" said those breeds were impossible to rehome. I disliked her, she never gave those breeds a chance. I never hardened to it, I cried in the loos afterwards.
OP, I will second the advice given re extending leads. All it takes is a split second, an inch or two off the pavement and that is it. After seeing two families go through the trauma of losing their dogs in this way, I'm not keen on them.
I hope your pup is okay, but second DBF's advice re socialising with bull breeds.
My lab was attacked several times in our local park, once by a lab, twice by a dalmation and once by a JRT. She was a rescue from work, battered and broken so much that it took three months of hospitalisation to heal her, and a further year working on basic training as she hadn't been trained at all. Now I'm having to start all over again with socialisation as she is so fearful. Please seek a good local class to take your dog to, your vet should be able to recommend a suitable one.
I hope everything works out okay for you.